copies: Keep changelog sidedata file open during copy tracing Instead of having a callback that opens and closes that file many times, a add and use a context manager method on the `revlog` class that keeps files open for its duration. Differential Revision: https://phab.mercurial-scm.org/D10888

purge: restore the `testedwith` declaration Otherwise, this extension gets highlighted as a 3rd party extension when an exception occurs. Differential Revision: https://phab.mercurial-scm.org/D10895

rust: remove dead utils module This was introduced a while back while not being imported anywhere in the module system. How pertinent this Facebook module was to the codebase was debatable at the time, nowadays with the Rust VFS layer having laid its foundations, it is clear that we should drop it. Differential Revision: https://phab.mercurial-scm.org/D10890

rebase: use str-keyed opts in remaining places Differential Revision: https://phab.mercurial-scm.org/D10892

rebase: keep str-keyed opts long enough to make `action` a str This is just another little py3 cleanup. Differential Revision: https://phab.mercurial-scm.org/D10891

benchmarks: restore `output` variable lost in D10884 Noticed by pyflakes (which I didn't have installed for Python 3.9 when I sent D10884). Differential Revision: https://phab.mercurial-scm.org/D10894

censor: implement censoring for revlogv2 It is a bit verbose and rough, but it works. Most of that logic can be common for `stripping`, so we can expect more refactoring of that code to accommodate both needs. However I wanted to keep this changesets "simple enough" and before moving forward. We also need to properly delete the older index/data/sidedata file, but this has implication for streaming clone and transaction, so this will come later. Differential Revision: https://phab.mercurial-scm.org/D10869

deltas: at a `target_rev` parameter to finddeltainfo Otherwise, recomputing a delta for a revision might result in a delta against a later revision or a full snapshot thinking we are appending a new revision. We will make use of this during censoring (and later, stripping). Differential Revision: https://phab.mercurial-scm.org/D10887

revlog: list older-but-still-around file in `files` These older files will eventually be removed, but we have to take them in account until they are. So we update `files` to keep fncache happy. Differential Revision: https://phab.mercurial-scm.org/D10868

revlog: add docket method to request new content files If we want to write content into new files, we need to be able to ask for them. Differential Revision: https://phab.mercurial-scm.org/D10867